Commercial services which employ a W-CDMA (Wideband Code division Multiple Access) method which is included in communication methods called a third generation were started in Japan since 2001. Furthermore, a service with HSDPA (High Speed Down Link Packet Access) which implements a further improvement in the speed of data transmission using downlinks (a dedicated data channel and a dedicated control channel) by adding a channel for packet transmission (HS-DSCH: High Speed-Downlink Shared Channel) to the downlinks has been started. In addition, services using an HSUPA (High Speed Up Link Packet Access) method have been started in order to further speed up uplink data transmission. The W-CDMA is a communication method which was determined by the 3GPP (3rd Generation Partnership Project) which is the organization of standardization of mobile communication systems, and the technical specification of the release 8 has been being organized currently.
In the 3GPP, as a communication method different from the W-CDMA, a new communication method having a wireless section, which is referred to as “Long Term Evolution” (LTE), and a whole system configuration including a core network, which is referred to as “System Architecture Evolution” (SAE), has also been studied. The LTE has an access method, a radio channel configuration, and protocols which are completely different from those of the current W-CDMA (HSDPA/HSUPA). For example, while the W-CDMA uses, as its access method, code division multiple access (Code Division Multiple Access), the LTE uses, as its access method, OFDM (Orthogonal Frequency Division Multiplexing) for the downlink direction and uses SC-FDMA (Single Career Frequency Division Multiple Access) for the uplink direction. Furthermore, while the W-CDMA has a bandwidth of 5 MHz, the LTE enables each base station to select one bandwidth from among bandwidths of 1.25, 2.5, 5, 10, 15, and 20 MHz. In addition, the LTE does not include a circuit switching method, unlike the W-CDMA, but uses only a packet communication method.
According to the LTE, because a communication system is configured using a new core network different from a core network (GPRS) in the W-CDMA, the communication system is defined as an independent radio access network which is separate from a W-CDMA network. Therefore, in order to distinguish from a communication system which complies with the W-CDMA, in a communication system which complies with the LTE, a base station (Base station) which communicates with a mobile terminal (UE: User Equipment) is referred to as eNB (E-UTRAN NodeB), and a base station control apparatus (Radio Network Controller) which performs exchange of control data and user data with a plurality of base stations is referred to as an EPC (Evolved Packet Core) (may be called aGW: Access Gateway). This communication system which complies with the LTE provides a unicast (Unicast) service and an E-MBMS service (Evolved Multimedia Broadcast Multicast Service). An E-MBMS service is a broadcast type multimedia service, and simply may be referred to as an MBMS. A large-volume broadcast content, such as news, a weather forecast, or a mobile broadcasting content, is transmitted to a plurality of mobile terminals. This service is also referred to as a point-to-multipoint (Point to Multipoint) service.
Matters currently determined in the 3GPP and regarding a whole architecture (Architecture) in an LTE system are described in nonpatent reference 1. The whole architecture (chapter 4 of nonpatent reference 1) will be explained with reference to FIG. 1. FIG. 1 is an explanatory drawing showing the configuration of a communication system using an LTE method. In FIG. 1, if a control protocol (e.g., RRC (Radio Resource Management)) and a user plane (e.g., PDCP: Packet Data Convergence Protocol, RLC: Radio Link Control, MAC: Medium Access Control, PHY: Physical layer) for a mobile terminal 101 are terminated at a base station 102, E-UTRAN (Evolved Universal Terrestrial Radio Access) is constructed of one or more base stations 102.
Each base station 102 carries out scheduling (Scheduling) and transmission of a paging signal (Paging Signaling, which is also referred to as paging messages (paging messages)) which is transmitted thereto from an MME 103 (Mobility Management Entity). The base stations 102 are connected to one another via X2 interfaces. Furthermore, each base station 102 is connected to an EPC (Evolved Packet Core) via an S1 interface. More specifically, each base station is connected to an MME 103 (Mobility Management Entity) via an S1_MME interface, and is also connected to an S-GW 104 (Serving Gateway) via an S1_U interface. Each MME 103 distributes a paging signal to one or more base stations 102. Furthermore, each MME 103 carries out mobility control (Mobility control) of an idle state (Idle State). When a mobile terminal is in any one of an idle state and an active state (Active State), each MME 103 manages a tracking area (Tracking Area) list. Each S-GW 104 carries out transmission and reception of user data to and from one or more base stations 102. Each S-GW 104 becomes a local mobility anchor point (Mobility Anchor Point) when a handover occurs between base stations. Furthermore, a P-GW (PDN Gateway) exists and carries out packet filtering for each user, allocation of a UE-ID address, etc.
Matters currently determined in the 3GPP and regarding a frame configuration in a LTE system are described in nonpatent reference 1 (Chapter 5). The currently determined matters will be explained with reference to FIG. 2. FIG. 2 is an explanatory drawing showing the configuration of a radio frame for use in a communication system using an LTE method. In FIG. 2, one radio frame (Radio frame) has a time length of 10 ms. Each radio frame is divided into ten equal-sized subframes (Sub-frames). Each subframe is divided into two equal-sized slots (slots). A downlink synchronization signal (Downlink Synchronization Channel Signal: SS) is included in each of the 1st (#0) and 6th subframes (#5) of each frame. Synchronization signals include a primary synchronization signal (Primary Synchronization Signal: P-SS) and a secondary synchronization signal (Secondary Synchronization Signal: S-SS). Multiplexing of a channel used for MBSFN (Multimedia Broadcast multicast service Single Frequency Network) and a channel used for other than MBSFN is carried out for each subframe. Hereafter, a subframe used for MBSFN transmission is referred to as an MBSFN subframe (MBSFN subframe). In nonpatent reference 2, an example of signaling at the time of allocation of MBSFN subframes is described. FIG. 3 is an explanatory drawing showing the configuration of an MBSFN frame. In FIG. 3, MBSFN subframes are allocated to each MBSFN frame (MBSFN frame). An MBSFN frame cluster (MBSFN frame Cluster) is scheduled. The repetition period (Repetition Period) of an MBSFN frame cluster is allocated.
Matters currently determined in the 3GPP and regarding a channel configuration in an LTE system are described in nonpatent reference 1. It is assumed that the same channel configuration as that used for non-CSG cells are used also for CSG (Closed Subscriber Group) cells. Physical channels (Physical channels) (chapter 15 of nonpatent reference) will be explained with reference to FIG. 4. FIG. 4 is an explanatory drawing explaining physical channels for use in a communication system using an LTE method. In FIG. 4, a physical broadcast channel 401 (Physical Broadcast channel: PBCH) is a downlink channel which is transmitted from a base station 102 to a mobile terminal 101. A BCH transport block (transport block) is mapped onto four subframes during a 40-ms time period. There is no clear signaling having a timing of 40 ms. A physical control channel format indicator channel 402 (Physical Control format indicator channel: PCFICH) is transmitted from the base station 102 to the mobile terminal 101. The PCFICH informs the number of OFDM symbols used for PDCCHs from the base station 102 to the mobile terminal 101. The PCFICH is transmitted in each subframe. A physical downlink control channel 403 (Physical downlink control channel: PDCCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PDCCH informs resource allocation (allocation), HARQ information about a DL-SCH (a downlink shared channel which is one of transport channels shown in FIG. 5), and a PCH (paging channel which is one of the transport channels shown in FIG. 5). The PDCCH carries an uplink scheduling grant (Uplink Scheduling Grant). The PDCCH also carries ACK/Nack which is a response signal showing a response to uplink transmission. The PDCCH is also called an L1/L2 control signal. A physical downlink shared channel 404 (Physical downlink shared channel: PDSCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. A DL-SCH (downlink shared channel) which is a transport channel and a PCH which is a transport channels are mapped onto the PDSCH. A physical multicast channel 405 (Physical multicast channel: PMCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. An MCH (multicast channel) which is a transport channel is mapped onto the PMCH.
A physical uplink control channel 406 (Physical Uplink control channel: PUCCH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The PUCCH carries ACK/Nack which is a response signal (response) which is a response to downlink transmission. The PUCCH carries a CQI (Channel Quality indicator) report. The CQI is quality information showing either the quality of received data or communication channel quality. The PUCCH also carries a scheduling request (Scheduling Request: SR). A physical uplink shared channel 407 (Physical Uplink shared channel: PUSCH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. A UL-SCH (an uplink shared channel which is one of the transport channels shown in FIG. 5) is mapped onto the PUSCH. A physical HARQ indicator channel 408 (Physical Hybrid ARQ indicator channel: PHICH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PHICH carries ACK/Nack which is a response to uplink transmission. A physical random access channel 409 (Physical random access channel: PRACH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The PRACH carries a random access preamble (random access preamble).
In a downlink reference signal (Reference signal), symbols known in the mobile communication system are inserted into first, third and final OFDM symbols of each slot. As measurement of a physical layer of each mobile terminal, there is reference symbol received power (Reference symbol received power: RSRP).
The transport channels (Transport channels) (chapter 5 of nonpatent reference 1) will be explained with reference to FIG. 5. FIG. 5 is an explanatory drawing explaining the transport channels for use in a communication system using an LTE method. Mapping between downlink transport channels and downlink physical channels is shown in FIG. 5A. Mapping between uplink transport channels and uplink physical channels is shown in FIG. 5B. In the downlink transport channels, a broadcast channel (Broadcast channel: BCH) is broadcast to all the base stations (cell). The BCH is mapped onto a physical broadcast channel (PBCH). Retransmission control with HARQ (Hybrid ARQ) is applied to a downlink shared channel (Downlink Shared channel: DL-SCH). Broadcasting to all the base stations (cell) can be carried out. Dynamic or semi-static (Semi-static) resource allocation is supported. Semi-static resource allocation is also referred to as persistent scheduling (Persistent Scheduling). DRX (Discontinuous reception) by a mobile terminal is supported in order to achieve low power consumption of the mobile terminal. The DL-SCH is mapped onto a physical downlink shared channel (PDSCH). A paging channel (Paging channel: PCH) supports DRX by a mobile terminal in order to enable the mobile terminal to achieve low power consumption. Broadcasting to all the base stations (cell) is requested. Mapping onto either a physical resource such as a physical downlink shared channel (PDSCH) which can be dynamically used for traffic, or a physical resource such as a physical downlink control channel (PDCCH) which is another control channel is carried out. A multicast channel (Multicast channel: MCH) is used for the broadcasting to all the base stations (cell). SFN combining of MEMS services (MTCH and MCCH) in multi-cell transmission is supported. Semi-static resource allocation is supported. The MCH is mapped onto a PMCH.
Retransmission control with HARQ (Hybrid ARQ) is applied to an uplink shared channel (Uplink Shared channel: UL-SCH). Dynamic or semi-static (Semi-static) resource allocation is supported. A UL-SCH is mapped onto a physical uplink shared channel (PUSCH). A random access channel (Random access channel: RACH) shown in FIG. 5B is limited to control information. There is a risk of collision. The RACH is mapped onto a physical random access channel (PRACH). HARQ will be explained hereafter.
HARQ is a technology of improving the communication quality of a transmission line by using a combination of automatic retransmission (Automatic Repeat reQuest) and error correction (Forward Error Correction). Retransmission provides an advantage of making an error correction function be effective also for a transmission line whose communication quality varies. Particularly, when performing retransmission, combining the results of reception of first-time transmission and the results of reception of retransmission provides a further improvement in the quality. An example of a retransmission method will be explained. When a receive side cannot decode received data correctly (when a CRC Cyclic Redundancy Check error occurs (CRC=NG)), the receive side transmits “Nack” to the transmit side. When receiving “Nack”, the transmit side retransmits the data. In contrast, when the receive side can decode the received data correctly (when no CRC error occurs (CRC=OK)), the receive side transmits “Ack” to the transmit side. When receiving “Ack”, the transmit side transmits the next data. There is “chase combining” (Chase Combining) as an example of a HARQ method. The chase combining is a method of transmitting the same data sequence at the time of first-time transmission and at the time of retransmission, and, when performing retransmission, combining the data sequence at the first-time transmission and the data sequence at the retransmission to improve the gain. This is based on an idea that even if the first-time transmission data has an error, the first-time transmission data partially includes correct data, and therefore the data can be transmitted with a higher degree of precision by combining the correct portion of the first-time transmission data and the retransmission data. Furthermore, there is IR (Incremental Redundancy) as another example of the HARQ method. The IR is a method of increasing the degree of redundancy with a combination with the first-time transmission by transmitting a parity bit at the time of retransmission to improve the quality by using an error correction function.
Logical channels (Logical channels) (chapter 6 of nonpatent reference 1) will be explained with reference to FIG. 6. FIG. 6 is an explanatory drawing explaining logical channels for use in a communication system using an LTE method. Mapping between downlink logical channels and downlink transport channels is shown in FIG. 6A. Mapping between uplink logical channels and uplink transport channels is shown in FIG. 6B. A broadcast control channel (Broadcast control channel: BCCH) is a downlink channel for broadcast system control information. The BCCH which is a logical channel is mapped onto either a broadcast channel (BCH) which is a transport channel, or a downlink shared channel (DL-SCH). A paging control channel (Paging control channel: PCCH) is a downlink channel for transmitting a paging signal. The PCCH is used when the network does not know the cell location of a mobile terminal. The PCCH which is a logical channel is mapped onto a paging channel (PCH) which is a transport channel. A common control channel (Common control channel: CCCH) is a channel for transmission control information between a mobile terminal and a base station. The CCCH is used when the mobile terminal does not have RRC connection (connection) between the mobile terminal and the network. In the downlink direction, the CCCH is mapped onto a downlink shared channel (DL-SCH) which is a transport channel. In the uplink direction, the CCCH is mapped onto an uplink shared channel (UL-SCH) which is a transport channel.
A multicast control channel (Multicast control channel: MCCH) is a downlink channel for point-to-multipoint transmission. The channel is used for transmission of MEMS control information for one or some MTCHs from the network to mobile terminals. The MCCH is used only for a mobile terminal currently receiving an MBMS. The MCCH is mapped onto either a downlink shared channel (DL-SCH) which is a transport channel, or a multicast channel (MCH). A dedicated control channel (Dedicated control channel: DCCH) is a channel for transmitting individual control information between a mobile terminal and the network. The DCCH is mapped onto an uplink shared channel (UL-SCH) in the uplink, and is mapped onto a downlink shared channel (DL-SCH) in the downlink. A dedicated traffic channel (Dedicate Traffic channel: DTCH) is a channel of point-to-point communications to each mobile terminal for transmission of user information. The DTCH exists for both the uplink and the downlink. The DTCH is mapped onto an uplink shared channel (UL-SCH) in the uplink, and is mapped onto a downlink shared channel (DL-SCH) in the downlink. A multicast traffic channel (Multicast Traffic channel: MTCH) is a downlink channel for transmission of traffic data from the network to a mobile terminal. The MTCH is used only for a mobile terminal currently receiving an MBMS. The MTCH is mapped onto either a downlink shared channel (DL-SCH) or a multicast channel (MCH).
A GCI is a global cell identifier (Global Cell Identity). In an LTE and in a UMTS (Universal Mobile Telecommunication System), a CSG cell (Closed Subscriber Group cell) is introduced. A CSG cell will be explained hereafter (Chapter 43.1 of nonpatent reference). A CSG (Closed Subscriber Group) is a cell (specified subscriber cell) in which an operator specifies subscribers which can use the cell. Each specified subscriber is allowed to access one or more E-UTRAN cells in a PLMN (Public Land Mobile Network). One or more E-UTRAN cells which each specified subscriber is allowed to access are referred to as “CSG cell (s)”. However, an access restriction is imposed on the PLMN. A CSG cell is a part of the PLMN which broadcasts a specific CSG identity (CSG identity: CSG ID, CSG-ID). Each subscriber group member that is registered in advance into a CSG cell and is allowed to access this CSG cell accesses the CSG cell by using the CSG-ID which is access allowance information. The CSG-ID is broadcast by the CSG cell or a cell. Two or more CSG-IDs exist for each CSG cell in the mobile communication system. A CSG-ID is used by each terminal (UE) in order to facilitate access from a CSG associated member. It has been debated in the 3GPP meeting that as the information broadcast by a CSG cell or a cell, a tracking area code (Tracking Area Code TAC) is used instead of a CSG-ID. A location track of a mobile terminal is carried out in units of each zone which consists of one or more cells. The location track is carried out in order to track the position of the mobile terminal even if this mobile terminal is in a state (idle state) which it not carrying out communications and to be able to call the mobile terminal (enable the mobile terminal to receive an incoming call). Each zone for this location track of the mobile terminal is referred to as a tracking area. A CSG white list (CSG White List) is a list in which all the CSG IDs of a CSG cell to which subscribers belong are recorded and which is stored in a USIM. The white list in each mobile terminal is provided by an upper layer. As a result, a base station of each CSG cell assigns radio resources to each mobile terminal.
A “suitable cell” (Suitable cell) will be explained hereafter (chapter 4.3 of nonpatent reference 4). A “suitable cell” (Suitable cell) camps on (Camp ON) in order for a UE to receive a normal (normal) service. (1) This cell has to be a part of a selected PLMN, a registered PLMN or a PLMN in an “Equivalent PLMN list”, and further satisfies the following requirement (2) in the latest information provided by NAS (non-access stratum). (1) The cell is not a barred cell. (2) The cell is not a part of a “barred LAs list for roaming” lists, but is a part of at least one tracking area (Tracking Area: TA). In this case, the cell has to satisfy above-mentioned (1). (3) The cell meets a cell selection evaluation criterion. (4) When the cell is specified, as a CSG cell, by system information (System Information: SI), the CSG-ID is a part of a “CSG white list” (CSG White List) of an UE (the CSG-ID is included in the CSG White List of the UE).
An “acceptable cell” (Acceptable cell) will be explained hereafter (chapter 4.3 of nonpatent reference 4). This cell camps on in order for a UE to receive a limited service (emergency dial). This cell satisfies all the following requirements. More specifically, a minimum set of requirements to start an emergency dial in an E-UTRAN network will be shown hereafter. (1) The cell is not a barred cell. (2) The cell meets a cell selection evaluation criterion.